Buffer overflow in Palo Alto Networks Cloud Ngfw
CVE-2026-0300
A buffer overflow vulnerability in the User-ID™ Authentication Portal (aka Captive Portal) service of Palo Alto Networks PAN-OS software allows an unauthenticated attacker to execute arbitrary code with root privileges on the PA-Series and…
Vulnerability class: Buffer Overflow
EPSS: 0.045 (89.4th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Palo Alto Networks Cloud Ngfw — versions All
- Palo Alto Networks Pan-os — versions 12.1.0, 11.2.0, 11.1.0
- Palo Alto Networks Prisma Access — versions All
- Paloaltonetworks Pa-1410
- Paloaltonetworks Pa-1420
- Paloaltonetworks Pa-3410
- Paloaltonetworks Pa-3420
- Paloaltonetworks Pa-3430
- Paloaltonetworks Pa-3440
- Paloaltonetworks Pa-410
Weakness classification (CWE)
CISA KEV (Known Exploited Vulnerabilities)
This CVE is on the CISA KEV catalog, added on . CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.
BOD 22-01 due date: .
Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Until the vendor releases an official fix, the following workaround should be implemented: - Restrict User-ID Authentication Portal access to only trusted zones. - Disable User-ID Authentication Portal if not required. 5/13/2026: Palo Alto has released a variety of patches. If these are relevant to your environment, please apply the designated patch.
Public proof-of-concept exploits
References
- psirt@paloaltonetworks.com (vendor-advisory, Mitigation, Vendor Advisory)
- 134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)
- 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e (Third Party Advisory)
Frequently asked questions
- What is CVE-2026-0300?
- CVE-2026-0300 is a critical-severity vulnerability in Palo Alto Networks Cloud Ngfw, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2026-05-06.
- How severe is CVE-2026-0300?
- Critical severity. CVSS v3 base score is 9.8 out of 10.
- Is CVE-2026-0300 known to be exploited?
- Yes. CVE-2026-0300 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-05-06), indicating it is being actively exploited. 9 public proof-of-concept repositories are indexed.